The present invention relates to semiconductor devices and, more particularly, to a five-terminal device with a dual channel structure having the function of a switching apparatus.
Numerous four layer semiconductor devices are commonly known in the art. These devices consist of four layers of semiconductor doped alternately with P-type and N-type impurities. Such devices include diodes, thyristors or silicon-controlled rectifiers, and bi-directional switches (diac and triac structures). These devices commonly have an outer P-type region called the anode and an opposite terminal of N-type region called the cathode. Alternating layers of N-type materials and P-type material are interposed between these terminals. These devices can functionally be considered as a single pole switch in that when biased with an external voltage applied to make the anode. positive with respect to the cathode, and appropriately triggered, current flows from the anode to the cathode. In a four layer diode, triggering occurs when the applied voltage exceeds a predetermined level.
The thrysistor or silicon-controlled rectifier is triggered through a control line commonly called a gate. The gate is connected typically to the inner P-type doped region and when a positive pulse is applied to the gate, regenerative action occurs within the device allowing current to flow from the anode to the cathode. In high-power thyristors, once the device is in the ON state, the gate circuit has little effect on the operation. However, in low-power thyristors, the gate circuit can be used to turn the device both on and off. Typically, a negative current is usually required to turn the device off.
Field-effect devices such as MOSFETs are also used to control current flow through a circuit. Briefly, an insulated gate is used to selectively control formation of a conductive channel between two terminals. In CMOS devices, two conductive channels of two transistor devices are alternately formed to connect the output to one of two other terminals. Essentially, the CMOS device comprises a PMOS transistor series connected to an NMOS transistor using the conductive material of the output terminal.